• Korean Journal of Medicinal Crop Science
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• v.26 no.1
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• pp.1-7
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• 2018

Background: Rehmanniae radix preparata (RRP) has been used as a traditional medicine and is one of the most important oriental herbal medicines. However, the physical characteristics of RRP are not suitable for use in industry. The present study was under-taken to determined the preparation method of RRP powder and the physicochemical characteristics of RRP powder by milling under different pre-freezing temperatures. Methods and Results: Moisture content, powder yield, particle size, bulk density, compressive stress, extraction yield, and 5-HMF content of PRR powders by milling with pre-freezing temperatures (-20, -40, -60, and $-80^{\circ}C$) were analyzed, and correlation among these factors was determined. Powder yield increased and particle size decreased in a pre-freezing temperature-dependent manner from -20 to $-60^{\circ}C$. The Hausner ratio increased from 1.186 to 1.225 with decreasing temperature from -20 to $-80^{\circ}C$, whereas compressive stress showed the opposite trend. Extraction yield and 5-HMF content were not significantly different between RRP powder. Significant correlations were observed among pre-freezing temperature and physical characteristics (e.g., yield, particle size, Hausner ratio, and compressive stress). Conclusions: These results suggest that the pre-freezing temperature is an important factor affecting the physical characteristics of PRR powder and applicable to the industrial production of RRP powder.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.204-210
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• 2004

Most auto-body members fabricated by the sheet metal forming process. During this process the thickness and material properties of the sheet metal are changed with the residual stress and plastic strain. This paper deals with the material properties of the sheet metal at the high strain rate considering the pre-strain effect. Specimens are selected from sheet metals for outer panels and inner members, such as SPCEN, SPRC45E, SPRC35R and EZNCD. The specimens are prepared with the pre-strain of 2, 5 and 10 % by tensile elongation in Instron 5583, which could be equivalent to the plastic strain in sheet metal forming. High speed tensile tests are then carried out with the pre-stained specimens at the strain rate of 1 to 100/sec. The experimental result informs that the material properties are noticeably influenced by the pre-strain when the yield stress of the specimens is moderate as SPCEN, SPRC35R and EZNCD. The result also demonstrates that the ultimate tensile strength as well as the yield stress is increased as the amount of the pre-strain is increased.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.453-463
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• 2018

Three points bending flexural test was modelled numerically to study the crack propagation in the pre-cracked beams. The pre-existing double internal cracks inside the beam models were considered to investigate the crack propagation and coalescence paths within the modelled samples. Notch configuration effects on the failure stress were considered too. This numerical analysis shown that the propagation of wing cracks emanating from the tips of the pre-existing internal cracks caused the final breaking of beams specimens. It was also shown that when two notches were overlapped, they both mobilized in the failure process and the failure stress was decreased when the notches were located in centre line. However, the failure stress was increased by increasing the bridge area angle. Finally, it was shown that in all cases, there were good agreements between the discrete element method results and, the other numerical and experimental results. In this research, it is tried to improve the understanding of the crack propagation and crack coalescence phenomena in brittle materials which is of paramount importance in the stability analyses of rock and concrete structures, such as the underground openings, rock slopes and tunnel construction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1335-1336
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• 2010

• International Journal of Concrete Structures and Materials
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• v.6 no.2
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• pp.79-85
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• 2012

This paper presents the differences in growth of time-dependent strain values in reinforced cement concrete (RCC) and pre-stressed concrete (PSC) flexural members through experiment. It was observed that at any particular age, the time-dependent strain values were less in RCC beams than in PSC beams of identical size and grade of concrete. Variables considered in the study were percentage area of reinforcement, span of members for RCC beams and eccentricity of applied pre-stress force for PSC beams. In RCC beams the time-dependent strain values increases with reduction in percentage area of reinforcement and in PSC beams eccentricity directly influences the growth of time-dependent strain. With increase in age, a non-uniform strain develops across the depth of beams which influence the growth of concave curvature in RCC beams and convex curvature in PSC beams. The experimentally obtained strain values were compared with predicted strain values of similar size and grade of plane concrete (PC) beam using ACI 318 Model Code and found more than RCC beams but less than PSC beams.

• Stress
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• v.26 no.4
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• pp.319-326
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• 2018

Background: This study investigated whether pre- and peri-disaster experiences influence on PostTraumatic Stress Disorder (PTSD) and whether post-disaster stress by life changes have impact on PTSD after controlling pre- and peri-disaster factors. Methods: Data came from a sample of 1,182 respondents who experienced natural disasters (flood and typhoon) in South Korea from 2012 to 2015. The SPSS Win 22.0 program was used for descriptive analysis, t-test, Chi-square test, Pearson's correlation and logistic regression analysis. Results: The results indicated that 24.3% of the disaster victims were in PTSD risk group. Compared with non-PTSD, PTSD risk group showed lower interpersonal trust and satisfaction, higher depression and anxiety, and lower subjective well-being. The results of hierarchical logistc regression revealed that all pre-, peri-, and post-disaster factors increased the probability of developing PTSD, except for relocation of residence. Moreover, a primary post-disaster predictor of PTSD was economic distress after controlling for pre- and peri-disaster. Conclusions: This study tested relative contributions of post-disaster factors on PTSD.

• The Journal of Korean Physical Therapy
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• v.33 no.3
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• pp.123-130
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• 2021

Purpose: Despite the existence of Snoezelen method, there is no case of researching the effects on game addiction. Therefore, this study aims to investigate the effects of Snoezelen therapy on stress, depression, anxiety and quality of life of college students who overuse computer games or mobile phone games. Methods: Eight students who responded to spend more than 30 hours of computer or mobile phone games in the selection questionnaire were recruited (The total respondents were 224 students). Students were randomly assigned to either the study group (4 students) or the control group (4 students). Stress (Korean version of Perceived Stress Scale, K-PSS), depression (Korean Screening Tool for Depression Disorders, K-DEP), Anxiety (Korean Beck Anxiety Inventory, K-BAI) and quality of life (Short Form Health Survey version 2 [SF-36]) were assessed three times (before intervention [pre], post-3 weeks [post 1], post-6 weeks [post 2]). Results: First, the study group (-4.75±3.86) and control group (1.00±2.71) showed significant difference (p<0.05) in the analysis of score changes between pre-test and test at 6 weeks (post 2) for K-DEP. Next, pre-test and test at 3 weeks of intervention (post 1) for K-BAI showed significant difference (p<0.05) in the study group (-2.50±1.91) and control group (2.25±2.99). In addition, pre-test and test at 6 weeks (post 2) showed significant difference (p<0.05) for the study group (-3.00±1.51) and control group (4.75±6.24). Conclusion: The study confirmed the possibility of Snoezelen therapy as a therapy method to induce effective responses in stress, depression, anxiety, and quality of life of college students with game addiction.

• Journal of People, Plants, and Environment
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• v.23 no.2
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• pp.245-254
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• 2020

Patients diagnosed with cancer face mental problems such as alienation, isolation, anxiety about death and fear, recovering from psychological difficulties. In this study, a forest healing program was provided for cancer patients to recover from psychological stress, depression, social isolation and self-esteem caused by cancer and changes in salivary cortisol through psychological and emotional recovery were measured. From September 19 to November 28, 2017, a forest healing program composed of a total of 10 sessions, two hours per session was provided for 12 cancer patients in the Forest of Taegyo located in Yongin. Psychological tests were performed with Social Adaptation Self-evaluation Scale (SASS), Korean-version Perceived Stress Scale (PSS) and Beck Depression Inventory (BDI) and the collected data were analyzed with the SPSS 18.0. The salivary cortisol level was measured along with the psychological tests and were analyzed by a specialized testing agency. The results of the analysis showed that the pre- and post-assessment score of SASS was 29.17 and 25.92, respectively, and that the pre- and post-assessment score of PSS was 30.50 and 23.92, respectively. The pre- and post-assessment score of BDI was 41.00 and 34.83, respectively, which showed significant differences. In addition, the pre- and post-assessment level of saliva cortisol was 3.13 and 1.68, respectively, showing a significant decrease. In short, the forest healing program was found to be effective in reducing physiological changes caused by social isolation and stress due to the emotional and psychological difficulties that the subjects who were diagnosed with cancer and were recovering from it have. In the future, it will be necessary to develop and implement a forest healing program by conducting a forest healing requirement survey on cancer patients.

• Journal of Families and Better Life
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• v.24 no.1 s.79
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• pp.83-102
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• 2006

The purpose of this study is to examine the effects of the divorce process on post-divorce adjustment. This study specifically examines the effects of the pre-divorce marital quality, perceived barriers to divorce at the time of considering divorce, and the level of everyday stress after divorce on post-divorce adjustment of men and women focused on gender differences. Data gathered from 147 men and 208 women living in Seoul and Gyeonggi province were analyzed for this study. The major findings are as follows. First, pre-divorce marital quality, perceived barriers to divorce at the time of considering divorce, and the level of everyday stress after divorce, have both positive and negative effects on post-divorce adjustment of divorced men and women depending on the stages of divorce process. Second, the relationship between various aspects of divorce process and adjustments differ according to the sub-dimension of post-divorce adjustment. Third, divorce process functions differently for divorced men and women. The results show the importance of considering the divorce process, including both pre-divorce and post-divorce circumstances in order to have a good understanding of post-divorce adjustment of men and women.